US2467201A - High-frequency induction heating coil - Google Patents

Description

April 12, 1949. R. D. FRAZIER 2,467,201

HIGH-FREQUENCY INDUCTION HEATING COIL Filed June 18, 1945 i Attorney.

v Varlf Patented Apr. 12, 1949 UNlTED HIGH-FREQUENCY INDUCTION HEATING COIL Richard D. Frazier, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application June 18, 1945, Serial No. 600,038

2 Claims. 1

My invention relates to high frequency heating coils and has for its object a simple and efiicient coil for heating convex or concave surfaces.

More particularly, my invention relates to the heating of metal parts for surface hardening purposes by high frequency currents having fre quencies up to 500,000 cycles a second or more. It is more specifically directed to the surface heating of metal articles passed continuously in heating relation with the coil, the article having a convex or concave surface to be heated.

In carrying out my invention in one form I provide a fiat spiral or pancake coil bent or shaped to fit the concave or convex surface to be heated.

For a more complete understanding of my invention reference should be had to the accompanying drawing, Fig. 1 of which is a fragmentary side elevation view of a high frequency heating coil embodying my invention applied to the heating of the beveled edge of a metal bar. Fig. 2 is an end elevation view of the apparatus shown in Fig. 1. Fig. 3 is a view similar to Fig. 1 showing a coil embodying m invention for heating the concave edge of a metal bar. Fig. 4; is an end view of Fig. 3, while Fig. 5 is a plan view of Fig. 3.

Referring to the drawing, I have shown my invention in one form in Figs. 1 and 2 as applied to the heating of the upper convex edge 5 of a steel bar 2, the edge I being beveled or pointed as seen in Fig. 2 with two plane surfaces positioned at an acute angle with each other.

For heating the upper edge I, I provide a coil 3 which is wound in the form of a fiat spiral coil and then bent along a diameter into two flat side portions 5 and 0, having substantially the same angular relation as the sides of the beveled edge I. This coil is mounted on a suitable electrically insulating support, not shown, to provide for the passage of the steel bar 2 under the coil, as shown in the drawing, with the two sides of the edge I in equally spaced substantially parallel relation with the two flat portions 5 and 6 of the coil.

During the heating operation the bar 2 is moved by suitable conveyor means, not shown, continuously at a predetermined speed from the right toward the left as seen in Fig. 1 and as indicated by the arrow I, while the coil 3 is en ergized from a suitable source of high frequency current supply, the terminals of which are connected to the terminals 8 and 9 of the coil. This source of high frequency current preferably is an electronic tube oscillation generator supplying current having a frequency of 500,000 cycles a second or more. The rate of movement of the bar 2 is adjusted relative to the rate of heating in such manner that when the bar is moved continuously at the predetermined speed the metal on the sides of the beveled portion I to a predetermined depth is heated to the decalescent or hardening temperature of the metal in passing along the coil.

As the heated portion of the bar moves out from under the coil it is immediately quenched to harden it by the application of a suitable cooling liquid such as water from a quenching device I0. This device consists of a U-shaped container having suitable apertures, not shown, in its in- I side wall. Water is supplied at a suitable pressure to this container I0 and is forced through the apertures onto the bar 2 thereby quickly to cool the metal of the beveled portion and harden it. For the purpose of providing a sharp line of demarcation for the quenching water thereby preventing the application of the water to the heating coil and the portion of the bar being heated, a baffle wall I I is provided together with a nozzle I2 for applying water to the side of the baffle opposite the heating coil. The water from the nozzle I2 flows down the outer side of the bafile II, the lower end of which is closely adjacent the beveled edge I and then onto the beveled edge, thereby to provide an initial cooling and hardening immediately after the heated beveled edge leaves the coil. The cooling is completed by the quench device I0.

Referring to Figs. 3, 4 and 5 in this application of my invention the steel bar It is provided with a concave upper edge I4 forming a longitudinal V-shaped notch in the edge of the bar with two plane surfaces positioned at an acute angle with each other. In the heating of this concave edge I have provided a coil I5 which is provided with two flat sides or portions I0 and I1 positioned at an angle with each other substantially the same as the angle between the surfaces of the notch I4. As shown clearly in Fig. 5, this coil consists in effect of two reversely wound elongated pancake or spiral coils. Thus, starting from the inner terminal I8 the conductor extends counterclockwise to form a plurality of substantially straight parallel lengths up to and including a central length I9 at the end of which the conductor is wound clockwise in a similar number of substantially parallel loops to the opposite inner terminal 20 of the coil.

As shown in the drawing the coil I5 is positioned by electrically insulating supporting means, not shown, with the central length I 9 f the coil adjacent the lowest point of the edge of the bar, i. e. opposite the junction of the two flat sides of the V-shaped notch and with the two portions it and I1 in equally spaced parallel relation with the sides of the notch.

In the operation of the apparatus, shown in Figs, 3, 4 and 5, the bar is moved from the righthand toward the left-hand in the direction of the arrow 2| of Fig. 3 at a predetermined speed, the

coil being energized with high frequency current having a frequency of 500,000 cycles a second or more. The bar is cooled after leaving the coil by water supplied by two nozzles 22 and 23 and a quenching device 24. The nozzles 22 and 23 are positioned at an acute angle with respect to each other to direct the flow of cooling water along the two plane surfaces of the V-shaped edge of the bar, Preferably the bar I3 is positioned with its left-hand end somewhat lower than its righthand end so that the cooling water flows in the V-shaped notch toward the left away from the coil and the portion being heated.

It will be observed that this reversely wound double pancake coil provides a plurality of substantially parallel straight side by side conductors at the center in which the current flows in the same direction. In the coil shown the two pairs of conductors 25 and 20, on opposite sides of the central conductor ill at the apex of the angle between the portions IB and I1, carry current flowing in the same direction as in the central conductor i9. This provides for the maximum magnetic flux in the walls of the notch and maximum heating eifect. While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto, since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A high frequency heating coil comprising a continuous electric conductor shaped into two reversely wound flat spiral coils having a plurality of substantially parallel side by side adjacent conductors forming adjacent sides of said coils in which a current in said conductor flows in the same direction, said coils being connected together by a central one of said parallel conductors.

2. A high frequency heating coil for heating a body having nonparallel intersecting surfaces comprising a continuous electric conductor shaped into two elongated reversely wound flat spiral coils having a plurality of substantially parallel straight side by side conductors adjacent each other in which a current in said conductor flows in the same direction, said coils being positioned in nonparallel relation with each other and connected together by a central one of said parallel conductors.

RICHARD D. FRAZIE-R.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,052,010 Bailey Aug. 25, 1936 2,075,079 Anderson Mar. 30, 1937 2,118,594 Douden May 24, 1938 2,14%,3'18 Kennedy Jan. 17, 1939 2,270,293 Grunder Jan. 20, 1942 2,308,240 Goodridge Jan. 12, 1943 FOREIGN PATENTS Number Country Date 541,155 Germany Jan. 11, 1932 OTHER REFERENCES Babat, Heat Treating and Forging, March 1941, pages 137, 138, and 139.

Electronics, October 1943, pages 112, 113, 299, and 300.

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